Twist drill grinding attachment



June 4, 1940. J. A. YANTISS 2,202,819

TWIST DRILL GRINDING ATTACHMENT Filed May 2, 1938 3 Sheets-Sheet 1 /a 30ZZ 7.2' 7 :3.

m W W&

ATTORNEYS June 4, 1940. J. A. YANTISS 2 3 TWIST DRILL GRINDINGATTACHMENT Filed May 2. 1938 3 Sheets-Sheet 2 Jana INVENTOR ATTORNEYSJune 4, 1940. A. YANTISS TWIST DRILL GRINDING ATTACHMENT Filed May 2,1938 .3 Sheets-Sheet 3 Zzss ATTO R N EYS ?atentati June 4, 1940 UNITEDSTATES PATENT OFFICE z,2o2,s9 'rws'r DRILL GRINDING ATTAcmmN'r JesseAlvin Yantiss, nana, Palestine Application May z, 1938, Serial No. zossz cams. (Cl. 51-219) This invention relates to twist drill grinders andmore particularly to an attachment to an ordinary hand or power operatedgrinding wheel.

The prime object of the invention is toproduce a simple yet practicaland highly eflicient device which may be readily applied to the toolrest or support in cooperative relation to a grinding wheel whereby toproperly grind the drill point so as to produce the proper eccentricityof the cutting iips of the drill end.

Another important object is to provide for adequate adjustment of theattachment and the drill supporting means thereof to properly positionthe cutting lip of the drill with relation to the face of the grindingwheel and also in correlation to the pivotal axis of the drillsupporting means.

A further object is to provide for the grinding of bits of differentdiameters.

With these and other objects to be attained as will hereinafter moreiully appear, the invention consists in the general Construction and inthe parts and combinations and arrangements of parts thereof, ashereinafter described and pointed out with particularity in the appendedclaims, reference being had to the accompanying drawings forming a partof the specication, and

` in which- Figure 1 is a plan view of one practical embodiment of theinvention in a device as applied to a hand operated grinder;

Figura 2 is an elevation viewed from one side of the device;

Figure 3 is an elevation viewed from the opposite side;

Figure 4 is a fragmentary view, on an enlarged scale, showing details ofthe pivotal mounting of the drill holding means and the correlation ofthe pivotal axis to the face of the grinding wheel and further detailsof the working support for the drill:

Figure 5 is a substantial cross section on the line 5--5 of Figure 4,showing an end view of the drill bit and its supporting collet holdingelement in the trough of the attachment;

Figure 6 is a perspective view of a gauge ele-- ment which may be usedin effecting the various adjustments of the attachments. Figure 7 is aside elevation of a modified form of the attachment;

Figure 8 is a section taken substantially on the line 3-3 of Figure 7;

Figure 9 is a fragmntary view, on an enlarged scale, illustratingdetails of the structure shown ,inFigure 7; and

` the inner side of the gear housing i3 is the grinding wheel i8 whichis mounted on the stub shaft is and driven by the gearing (not shown) insaid housing l 3 by means of the crank on the outer 35 side of thecasing.

Mounted on the tool support 2| o! the grinder adjacent the periphery ofthe wheel !8 is a block 22 of substantial thickness and or generalrectangular form. As shown, this block 22 has a re- 20 duced end portion23 which rests on the tool-support or shelf 2! and is clamped thereto byan ordinary vise, said vise, as shown, including an elongated shani: orstem portion 24 having an arm 25 overhanging the top of the blockportion 25 23, said stern or shank portion being longitudinallyadjustable in a lower arm 26 which letter has a clamping screw 21working therein andprovided with a head 28 at its upper end engaging theunder side of the tool support or shelf z, ai) said screw element 21having an elongated handle 29 at its lower end. said block 22, which asabove noted, is of substantial thickness, provides a rigid supportingbody for the drill grinding attachment of the present invention and itsrelative adjustability on the tool support is an important feature ofthe present invention as will later more fully appear.

Pivotally mounted on the inner face of the block 22, as at 30, is aplate 3| having an arcuate end portion 32 which is formed on a radiusfrom the pivotal axis 30, said arcuate edge portion 32 abutting a stopscrew or stud 33 projecting beyond the inner face of the .block 22 inthe path of the upper and lower lugs 34 projecting from 5 the end of theplate 3i at the opposite terminals of said arcuate end portion 32 ot theplate for limiting the swinging movement of said plate 3I on itspivot`30.

Provided integrally or otherwise on the face of 50 the plate 3i is anangular bracket 35, on the diagonal marginal portion 36 of which atrough 31 is rigidly attached. This trough, which has right angular sidewalls, is open at its inner end but is closed by a wall 38 ofsubstantial thickness at its ,u

In carrying' out the present invention, inter-- changeable collets ordrill holding chucks are provided, said collets being of the sameexternal dimensions but having axial bores of various diametersrespectively corresponding to the different diameters of drills to beground. These collets, one of which is shown in detail in Figure 4 ofthe drawings, each comprise a forwardly tapered head portion 4l which isjoined by a reduced neck 42 to a rearwardly tapered shank portion 43,said shank portion being split longitudinally throughout its length soas to be received in the bore 44 of an elongated holder 45, one endportion of the bore 44 being reduced. as at 46, and into which portionthe end of the collet enters with wedging' eil'ect whereby to securelyclamp the inserted drill bit 41 against both rotative and endwisemovement in the collet and also to prevent rotation of the collet insaid holder 45.

The holder 45, as shown. is of square cross section so as to fit withinthe trough 31 without rotation but is capable of endwise movementtherein so that the drill bit end may be pressed against the face of thegrinding wheel s as will be presently described.

In setting up the attachment the block 22 is adjusted on the toolsupport 2| so that the axis of the pivot 30 is a definite distance fromthe inner side face of the grinding wheel IB, which distance is governedby the diameter of the drill to be sharpened and the character of thematerial on which the sharpened drill is to be used. For example, whenthe drill is to be used on iron or steel the distance between the faceof the grinding wheel and the pivot center should be approximatelyone-fifth less than the diameter of the drill, whereas for brass orcopper said distance should be approximately one-third less than thediameter of the drill. The nearer the pivot center is to the grindingwheel the keener will be the angle of the cutting lips on the drill assharpened.

In the ordinary twist drill there are two opposed cutting lips, and forideal performance in the drilling operation it is essential that each ofsaid lips be ground with uniformity and exactness as to angularity andlength thereof and this is accomplished by the use of the attach-,

ment of the present invention.

The drill bit 41 having been placed in the collet and the latteradjusted in the holder and the holder placed in the trough 31 with theprotruding cutting end of the bit in abutting relation to the face ofthe grinding wheel s the trough is slowly raised from its loweredposition by one hand of the operator while turning the crank 20 with hisother hand to rotate the grinding wheel |8 and at the same time exertingpressure with the ngers 'of the hand which is lifting the trough wherebyto rmly retain the holder 45 in the trough. In this connection, it isnoted that the screw element 39 is adjusted to prevent outward endwisemovement of the holder 45 in the trough 21 either by direct contactbetween the adlacent end of the holder 45 asoaec and said screw 39 or,in cases where the holder 45 is not of suflicient length to engage saidscrew element 39, a filier block 45 of* wood or metal may be interposedbetween the end of the said holder 45 and said screw element 39. asshown in Figures 1 and 2 of the drawings. The provision of this setscrew 39 is for the primary purpose of maintalning the drill bit i'n thesame endwise relation to the face ot the grinding wheel s when theholder 45 is turned over and replaced in the trough 31 to grind thesecond cutting lip.

While the trough 31 is mounted in fixed angular relation to the pivotedsupporting plate Il. and the block 22, in the set up of the attachment,is disposed at right angles to the face of v the grinding wheel s, it isnoted that some comparativeiy close relative adjustment between thepivotal axis 30 of the plate 3! and the face of the grinding wheel !8 isnecessary to properly position the cutting lip of the drill bit withrelation to said pivotal axis 30, and to facilitate such adjustment aspecial gauge 49 may be provided as shown in Figure 6 of the drawings.This gauge, as shown, is of the general form of an ordinary L-shapedsquare having one long leg and a short right angular leg 5l, the outerright angular margins being used to square the block 22 with thegrinding wheel !5. purpose is attained by providing scales at theopposite ends of the square 49 for measuring the distance between thepivot center and the face of the grinding wheel. These Scales,designated generally by the numeral 52 may be marked to indicatemillimeters or fractions of an inch, say. thirty-seconds. There is athird use for the scale in that the inner portion of the short leg 5i isbeveled oil?, as at 53, and utilized for testing the height of thecutting lip of the drill bit in relation to the pivotal center of theplate SI. That is to say, this beveled portion 53 is of a length fromthe adjacent longitudinal side of the longer leg 50 corresponding to thedistance from the top of the block 22 to the pivotal center 30 of theplate 3l so that, by resting the longer leg 50 across the top of theblock 22 with the portion 53 depending above the end of the drill bit,it is readily determined if the cutting lip of the drill bit is inproper relation to the pivotal axis when the trough containing the drillbit is in uppermost raised position. In this connection, it is notedthat the cutting lip must not be any higher than the pivotal center butshould be as close to such center as possible, although if a triflethereunder no harm will occur. If the cutting lip is too low the holder45 may be raised in the trough 31 by the insertion of a shim or sh'mstherebetween. For this purpose it has been found practical to utilizethick paper or cardboard sheets of proper length and width which arescored on a median longitudinal line and bent to fit as a lining in thetrough, or, obviously, sheet metal may be used for this purpose.

Instead of detachably securing the r'nain supporting block 22 on thetool rest or support 2! of the grinder as in the construction andarrangement hereinbefore described, a corresponding supporting block 22'of somewhat different polygona form, but having a similarly squared topedge portion secured firmly to the under side of the tool rest 2i' bysuitable machine screws or bolts 54, is provided (see Figures 7 and 9).

Another Preferably, as shown, this block 22' has its opclearancefor theoperator's hands in manipulating the drill supporting trough 31 and'operating the crank 20 to rotate the grinding wheel BO. In thismodification, instead of shiftlng the block 22' on the tool rest orsupport !I to vary thedistance between the pivotal axis of the troughcarrying plate :I and the face of the grinding wheel !8, an adjustablepivot is provided on said blockl' for said plate 3l. As shown moreclearly in Figure 10, this pivot comprises a stud which is provided withan axial bore through which a stub shaft 56 on the plate a extends, saidstub shaft '58 having a retaining nut 51 at its outer end abutting theouter end of said stud 55 with a Washer B! interposed therbetween. Thestud 55 is extended through a horizontal elongated slot 59 in said block22' and it is provided at its inner end with a squared head 60 which isset in a rectangular countersink BI in the inner face of said block 22and surrounding said elongated slot 59, the head 60 being fiush with theface of the block and by its slidable fitting in said countersink Blpreventing turning of the stud 55, yet permitting said stud to beadjusted lengthwise of said slot 59. The outer end portion of said stud55 is externally screw threaded for the reception of a retaining nut 62which is tightened against the outer face of the block 22' to hold thestud in'its respective adjusted positions in said slot 59.

Obviously, to conorm to the adjustment of the pivot hearing stud 55 astop stud 33' corresponding to the herelnbefore described stop stud 33for limiting the swinging movement of said plate 3! must be accordinglyprovided. This stud 33', as shown more clearly in Figure 8, is extendedthrough a longitudinal slot 53 in said block 22' and it is provided witha collar ti adjacent its projecting inner end portion, said collar beingreceived in a countersink 55 in the inner face of said block 22' andsurrounding said siot 53, the outer end portion of said stud 33' beingscrew threaded, as at 66, and provided with a wing nut t? which istightened against the outer face of said block 22' to lock the stud inits adjusted position.

Other than the diiference in the pivotal mounting and stop provisionsfor the movement of the plate ai, said plate isthe same in character asin the hereinbefore described modification, as are the trough t'i andthe several drill holding elemente employed in the use of theattachment.

In order to facilitate the proper positioning ofthe drill bit withrelation to the holder 45 for the proper presentation of the drill pointto the face of the grinding wheel i@ the holder 45 is provided at itsend with marks 88 extending diagonally from opposite corners to the boreopening u. By this provision, before the collet 4| is tightened in thebore of the holder 15, the bit n is turned to align its opposite lipportions with said marks tt, and after the bit has been so positionedthe inner end of the holder 45 may be tapped with a hammer or otherinstrument or strucl; against a solid object so that the collet with'the bit therein is moved towards that end of the holder and becomeswedged in the reduced portion it of the bore, thereby tightly clampingthe drill bit and the collet with the bit tlus clamped being securelyheld against rotation in the holder while the grinding operation isbeing performed. So, too, for the convenience of the operator indifferentiatng between the two cutting lips so there can be no mistakeas to which lip has been ground after placing the holder in the trough31, suitable distiguishing marks may be provided on opposite sides ofthe holder. For this purpose it has been found practical to provide asingle dot 69 on one side and two dots on the opposite side. one ofwhich, of'

prising in combination' with a grinding unit including a grinding wheeland a tool rest, a supporting block mounted on said tool rest instationary working position perpendicularly to the flat side face of thegrinding wheel, a plate swingably mounted on the inner face portion ofsaid supporting block about an axis relatively adjacent the side face ofthe grinding wheel and,

at right angles to the axis of said wheel, stop means for restrictingthe movement of said swingable plate, a trough member rigidly mounteddiagonally on said swingable plate and movable with said plate and incorrelation to the opposed side face of the grinding wheel, said troughbeing of right angular cross-section and drill holding means removablyand reversibly fltting said trough, said means including an elongatedholder element corresponding in square cross-section to the form of saidtrough whereby to be nonrotatable but movable endwise in the trough,said holder element having an axial bore, a bit receiving and retainingcollet receivable in the bore of said holder element, and an adjustableabutment in said trough for the outer end of said holder element, thedistance between the side face of the grinding wheel and the pivotalaxis of said swingable plate and between said pivotal axis and thecutting lip of the drill end when applied to the face of the grindingwheel, and with said plate in its uppermost position, being such thatthe working contour of the bit end is formed and the angularity of thecutting lips is defined during the upward swinging movement of the plateand by reversal of the holder element a half turn about its longitudinalaxis to separately grind each duplicately formed half of the cutting endof a conventional twist drill bit.

2. A grinding attachment for drill hits, comprising in combination witha grinding unit including a grinding wheel and a tool rest, a stationarysupporting block mounted on said tool rest and extending perpendicularlybeyond one fiat side of the 'grinding wheel in parallel relation to theaxis of said wheel, a pivot hearing on said supporting block, the axisof said bearing being at right angles to the axis ofthe grinding wheeland said hearing being adjustable on said block whereby to vary thedistance between the 'axis of the hearing and the adjacent side face ofthe grinding wheel, a plate swingably mounted on said pivot hearing inslidable contact with the inner face of said supporting block,adjustable stop means for limiting the up-anddown movement of saidplate, the adjustment of said means corresponding to the adjustment ofsaid pivot hearing, a trough member mounted' dlagonally on said platewith its inner end adjacent said pivot hearing and spaced from theopposed sldeface of the grindlng wheel. an adjustable abutment at theouter end of said trough member, and removable and reversible drlllholding means flttng said trough with endwse movement but non-rotatvetherein, the bit in said drlll hodlng means being projected intoengagementwith the !ece of the srinding whee with the cutting lip of thebit in parane! reltlon to the face of the wheel and in substantilly thesame plane as the axs of seid pivot hearing.

mssn ALVIN nmes.

